The present invention relates generally to solutions for scanning a touch screen in search of objects positioned on the screen to indicate input commands. More particularly the invention relates to an interface arrangement according to the preamble of claim 1, a mobile terminal according to the preamble of claim 9 and a method of generating input commands according to the preamble of claim 10. The invention also relates to a computer program product according to claim 17 and a computer readable medium according to claim 18.
The current trend in mobile and portable devices is that the devices are made physically smaller and smaller. At the same time, the devices are provided with more functionality and processing capacity. Therefore, flexible user interfaces are required to enable efficient input of commands and data, while allowing presentation of complex information. To this aim, touch screens and other types of multi-purpose interface means are highly useful.
US 2004/0263482 discloses a touch screen arrangement for a mobile telephone. Here, in addition to a display unit, the touch screen includes a number of light pulse emitting elements and a number of light receiving elements, which are arranged along the edges of the display unit. The emitting elements generate light pulses according to a predetermined sequence, and based on light energy registered by the receiving elements, it is determined whether or not a light-obstructive object (e.g. a fingertip) is present on the display unit. Hence, user-generated commands can be fed into the telephone.
However, depending on the conditions in which the telephone is operated the energy level received by the light receiving elements may vary substantially. For instance, when operated in direct sunlight, the received energy level is typically many factors of ten higher than the energy level received when the unit is operated in a dark or shaded environment.